The OregonianMayor Sam Adams will support fluoridating the city's water, ensuring it will pass the Portland City Council.

Portland Mayor Sam Adams on Friday used his Twitter account to announce that he'll vote in favor of a proposal to fluoridate the city's drinking water.

Adams' decision gives fluoride proponents three votes, with commissioners Randy Leonard and Nick Fish already voicing their support. No vote has been scheduled, although its expected the proposal would head to the Portland City Council in September.

At about 2:30 p.m., Adams responded to a Tweet asking him to vote in favor of fluoridation by writing: "I will." He confirmed later on Twitter that his vote ensures a majority, which would lead to fluoridating a water supply serving about 900,000 residents in Portland, Gresham, Tigard and Tualatin.

Adams decision came 27 hours after his spokeswoman said he hadn't made up his mind.

"The mayor is currently researching the topic and looks forward to hearing feedback from Portlanders before he makes a decision," Caryn Brooks told The Oregonian.

Estimates from the Portland Water Bureau put the tab for fluoridation at about $5 million and officials wrote in a memo that it would take five years for the program to launch.